U.S. patent number 7,487,235 [Application Number 10/669,870] was granted by the patent office on 2009-02-03 for dynamically varying a raid cache policy in order to optimize throughput.
This patent grant is currently assigned to Dell Products L.P.. Invention is credited to Carlton A. Andrews, Thomas Vrhel, Jr..
United States Patent |
7,487,235 |
Andrews , et al. |
February 3, 2009 |
Dynamically varying a raid cache policy in order to optimize
throughput
Abstract
In an information handling system, an application operating on
an elements of a the information handling system having one or more
RAID systems is used to monitor the number of client devices and
other operational aspects of the system. The application is
constructed and arranged to determine and implement the best cache
policy for the RAID systems in order to maximize the desired
operational characteristics of the information handling system. The
application can operate on a single server or RAID system device,
or the application can operate on a separate device to control the
cache policies of one or more servers.
Inventors: |
Andrews; Carlton A. (Austin,
TX), Vrhel, Jr.; Thomas (Woodinville, WA) |
Assignee: |
Dell Products L.P. (Round Rock,
TX)
|
Family
ID: |
34393435 |
Appl.
No.: |
10/669,870 |
Filed: |
September 24, 2003 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20050076115 A1 |
Apr 7, 2005 |
|
Current U.S.
Class: |
709/223;
707/999.2; 709/224; 709/226; 711/114; 711/118 |
Current CPC
Class: |
H04L
67/1008 (20130101); H04L 67/1002 (20130101); H04L
67/1025 (20130101) |
Current International
Class: |
G06F
15/173 (20060101); G06F 12/00 (20060101); G06F
17/30 (20060101) |
Field of
Search: |
;709/226,223,224
;707/200 ;711/114,118 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Follansbee; John
Assistant Examiner: Chea; Philip J
Attorney, Agent or Firm: Baker Botts L.L.P.
Claims
What is claimed is:
1. An information handling system comprising: a server, said server
having one or more RAID systems, said RAID systems capable of
implementing two or more cache policies, wherein at least one or
said cache policies is an adaptive policy based on previous
activity in the information handling system; a network operative
with said server, said network connection one or more clients to
said server, said clients constructed and arranged to communicate
with said server thereby placing a load on said server; a load
monitor operative with said one or more RAID systems, said load
monitor constructed and arranged to monitor said load, said load
monitor further constructed and arranged to select one or more
cache policies of said one or more RAID systems that optimize a
performance characteristic of said information handling system,
wherein said load monitor monitors said load and implements a cache
policy that optimizes said characteristic of said information
handling system; a storage accessible by said load monitor, wherein
said storage comprises one or more tables of stored information
accessible by said load monitor, wherein the stored information of
each of the one or more tables relates to a total number of active
clients and one or more cache settings; wherein the one or more
tables of stored information form one or more templates; and
wherein said load monitor employs the one or more templates and an
algorithm to select said one or more cache policies.
2. The information handling system according to claim 1, wherein
said RAID system has a read cache.
3. The information handling system according to claim 2, wherein
said read cache has a no-ahead policy.
4. The information handling system according to claim 2, wherein
said read cache has an adaptive policy.
5. The information handling system according to claim 2, wherein
said read cache has a read-ahead policy.
6. The information handling system according to claim 1, wherein
said RAID system has a write cache.
7. The information handling system according to claim 6, wherein
said write cache has back policy.
8. The information handling system according to claim 6, wherein
said write cache has through policy.
9. The information handling system according to claim 1, wherein
said RAID system has an I/O.
10. The information handling system according to claim 9, wherein
said I/O has a cached policy.
11. The information handling system according to claim 9, wherein
said I/O has a direct policy.
12. The information handling system according to claim 1, wherein
one of said cache policies is a no-ahead policy.
13. The information handling system according to claim 1, wherein
one of said cache policies is a read-ahead policy.
14. The information handling system according to claim 1, wherein
one of said cache policies is back policy.
15. The information handling system according to claim 1, wherein
one of said cache policy is a through policy.
16. The information handling system according to claim 1, wherein
said cache policy is a cached policy.
17. The information handling system according to claim 1, wherein
said load monitor is a load balancer.
18. The information handling system according to claim 1, wherein
said load monitor is a router.
19. The information handling system according to claim 1, wherein
said load monitor is a server.
20. The information handling system according to claim 1, wherein
said load monitor is a cluster master.
21. An information handling system comprising: at least one server,
sand at least one server having one or more RAID systems, said RAID
systems capable of implementing two or more cache policies, wherein
at least one of said cache policies is an adaptive policy based on
previous activity in the information handling system; a network
operative with said server, said network connecting one or more
clients to said server, said clients constructed and arranged to
communicate with said server thereby placing a load on said server;
a load balancer, said load balancer constructed and arranged to
allocate said load among said one or more servers; and a load
monitor operative on said load balancer, said load monitor
constructed and arranged to monitor said load, said load monitor
further constructed and arranged to select a cache policy of said
one or more RAID systems on said one or more servers that optimize
said performance characteristic of said information handling
system, wherein said load monitor monitors said load and implements
a cache policy that optimizes a characteristic of said information
handling system; a storage accessible by said load monitor, wherein
said storage comprises one or more tables of stored information
accessible by said load monitor, wherein the stored information of
each of the one or more tables relates to a total number of active
clients and one or more cache settings; wherein the one or more
tables of stored information form one or more templates; and
wherein said load monitor employs the one or more templates and an
algorithm to select said one or more cache policies.
22. The information handling system according to claim 21, wherein
said load monitor is a load balancer.
23. The information handling system according to claim 21, wherein
said load monitor is a router.
24. The information handling system according to claim 21, wherein
said load monitor is a server.
25. The information handling system according to claim 21, wherein
said load monitor is a cluster master.
Description
BACKGROUND OF THE INVENTION TECHNOLOGY
1. Field of the Invention
The present invention is related to information handling systems,
and more specifically, to optimizing the throughput of data by
modifying RAID cache parameters based on real-time operating
conditions.
2. Description of the Related Art
As the value and use of information continues to increase,
individuals and businesses seek additional ways to process and
store information. One option available to users is information
handling systems. An information handling system generally
processes, compiles, stores, and/or communicates information or
data for business, personal, or other purposes, thereby allowing
users to take advantage of the value of the information. Because
technology and information handling needs and requirements vary
between different users or applications, information handling
systems may also vary regarding what information is handled, how
the information is handled, how much information is processed,
stored, or communicated, and how quickly and efficiently the
information may be processed, stored, or communicated. The
variations in information handling systems allow for information
handling systems to be general or configured for a specific user or
specific use such as financial transaction processing, airline
reservations, enterprise data storage, or global communications. In
addition, information handling systems may include a variety of
hardware and software components that may be configured to process,
store, and communicate information and may include one or more
computer systems, data storage systems, and networking systems,
e.g., computer, personal computer workstation, portable computer,
computer server, print server, network router, network hub, network
switch, storage area network disk array, RAID disk system and
telecommunications switch.
RAID disk systems have been employed in the prior art to provide an
inexpensive way to store information reliably. Typical RAID disk
arrays are composed of one or more hard disks with some extra logic
that dictates where the information is to be distributed among the
hard disks. Generally, a given piece of information is distributed
to two or more hard disks so that if one disk becomes inoperative,
the given piece of information is available on a second or third
hard disk. The chance that two or more hard disks will become
inoperative simultaneously, while possible, is remote.
In order to perform the distribution during write operations (and
consequently in many read operations), many RAID disk systems
employ a caching procedure. The choice of cache procedure is often
based on the preference of the manufacturer, or the user. The
choice is often based on some particular network bandwidth
bottleneck that is perceived by the network administrator. Other
choices are simply set by the vendor and "hard coded" into the RAID
controller.
Vendors often struggle with determining which of several cache
options to offer their customers. Similarly, network administrators
struggle to choose among the cache policies available. The choice
of which cache policy has important ramifications for overall
network performance. Poorly chosen cache policies can cause the
RAID disk system to take longer to satisfy read and write
operations imposed by network clients, leading to unnecessary
network congestion and lower overall network system
performance.
Therefore, a problem exists, and a solution is required for
improving the operational performance of RAID arrays.
SUMMARY OF THE INVENTION
The present invention remedies the shortcomings of the prior art by
providing a method, system and apparatus, in an information
handling system, for monitoring a set of conditions, such as the
number of connected clients on a network, their open files, and
input/output ("I/O") requests. Based on the conditions, and
previous measurements made for the same class of machine that
supports the clients, the RAID cache parameters can be altered
dynamically through, for example, the application programming
interface ("API") that is provided by the vendor of the RAID
controller. Calls to the API can be used to provide maximum disk
throughput as clients request and release control of their files on
the system.
Alternate embodiments of the present invention enable the
monitoring of whether the client's files are actively requesting
data from files that have been requested (by other clients) or have
been released by other clients.
Yet another alternate embodiment of the present invention, a
process on each server performs the monitoring functionality
mentioned above. The server process measures the conditions of the
network, and adjusts dynamically, the cache parameters of the
server's RAID controller in order to maximize throughput of the
mass storage devices associated with the server's RAID array.
Still another embodiment of the present invention utilizes a
process on, for example, a load balancer, server, router, grid or
cluster master to monitor the conditions of the network and adjust
dynamically the cache parameters of the RAID arrays for one or more
servers or other devices providing storage for the network.
Other technical advantages of the present disclosure will be
readily apparent to one skilled in the art from the following
figures, descriptions, and claims. Various embodiments of the
invention obtain only a subset of the advantages set forth. No one
advantage is critical to the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the present disclosure and
advantages thereof may be acquired by referring to the following
description taken in conjunction with the accompanying drawings
wherein:
FIG. 1 is a schematic block diagram of an exemplary embodiment of
an information handling system;
FIG. 2 a is graph indicating the bandwidth affects of two different
RAID settings for different numbers of clients;
FIG. 3 a is graph indicating the bandwidth affects of two different
adaptive channels for different numbers of clients;
FIG. 4 is a flowchart illustrating an embodiment of the method of
the present invention;
FIG. 5 is a block diagram illustrating an network of clients and
servers that implement an embodiment of the present invention;
and
FIG. 6 is a block diagram of another exemplary embodiment of the
present invention.
FIG. 7 is a block diagram of another exemplary embodiment of the
present invention.
The present invention may be susceptible to various modifications
and alternative forms. Specific exemplary embodiments thereof are
shown by way of example in the drawing and are described herein in
detail. It should be understood, however, that the description set
forth herein of specific embodiments is not intended to limit the
present invention to the particular forms disclosed. Rather, all
modifications, alternatives, and equivalents falling within the
spirit and scope of the invention as defined by the appended claims
are intended to be covered.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
For purposes of this disclosure, an information handling system may
include any instrumentality or aggregate of instrumentalities
operable to compute, classify, process, transmit, receive,
retrieve, originate, switch, store, display, manifest, detect,
record, reproduce, handle, or utilize any form of information,
intelligence, or data for business, scientific, control, or other
purposes. For example, an information handling system may be a
personal computer, a network storage device, or any other suitable
device and may vary in size, shape, performance, functionality, and
price. The information handling system may include random access
memory (RAM), one or more processing resources such as a central
processing unit (CPU), hardware or software control logic, ROM,
and/or other types of nonvolatile memory. Additional components of
the information handling system may include one or more disk
drives, one or more network ports for communicating with external
devices as well as various input and output (I/O) devices, such as
a keyboard, a mouse, and a video display. The information handling
system may also include one or more buses operable to transmit
communications between the various hardware components.
Referring now to the drawings, the details of an exemplary
embodiment of the present invention are schematically illustrated.
Like elements in the drawings will be represented by like numbers,
and similar elements will be represented by like numbers with a
different lower case letter suffix.
Referring to FIG. 1, depicted is an information handling system
having electronic components mounted on at least one printed
circuit board (PCB) (not shown) and communicating data and control
signals there between over signal buses. In one embodiment, the
information handling system is a computer system. The information
handling system, generally referenced by the numeral 100, comprises
processors 110 and associated voltage regulator modules (VRMs) 112
configured as a processor node 108. There may be one or more
processor nodes 108 (two nodes 108a and 108b are illustrated). A
north bridge 140, which may also be referred to as a "memory
controller hub" or a "memory controller," is coupled to a main
system memory 150. The north bridge 140 is coupled to the
processors 110 via the host bus 120. The north bridge 140 is
generally considered an application specific chip set that provides
connectivity to various buses, and integrates other system
functions such as memory interface. For example, an Intel 820E
and/or 815E chip set, available from the Intel Corporation of Santa
Clara, Calif., provides at least a portion of the north bridge 140.
The chip set may also be packaged as an application specific
integrated circuit ("ASIC"). The north bridge 140 typically
includes functionality to couple the main system memory 150 to
other devices within the information handling system 100. Thus,
memory controller functions such as main memory control functions
typically reside in the north bridge 140. In addition, the north
bridge 140 provides bus control to handle transfers between the
host bus 120 and one or more other buses, e.g., PCI bus 170 and AGP
bus 171, the AGP bus 171 being coupled to video display 174. The
second bus may also comprise other industry standard buses or
proprietary buses, e.g., ISA, SCSI, USB buses 168 through a south
bridge (bus interface) 162. These secondary buses 168 may have
their own interfaces and controllers, e.g., RAID storage system 160
and input/output interface(s) 164. The RAID storage system 160 may
contain one or more sub-components. For example, the RAID storage
system 160 may contain one or more RAID controllers, and one or
more disk drives (often called "arrays") that are operative with
the RAID controller. Other RAID storage systems 160 may contain
only one or more mass storage devices which are controlled
(striped) by software operating within, for example, an operating
system kernel such as LINUX.RTM. which is available on the Internet
at kernel.org. Alternatively, the RAID controller may be in the
form of hardware that is embedded within one or more chips on a
motherboard, or on a peripheral card that is connected to the
motherboard by, for example, a PCI connector. Other RAID
controllers can use a combination of hardware and software.
Alternate embodiments of the information handling system of the
present invention provide a RAID system separate from the
computers, servers and clients that it serves. Such a separate RAID
system is illustrated in FIG. 7. In the illustrative example of
FIG. 7, the information system 700 has two or more separate
elements, namely the server 712 (which could also be a client
workstation or other device) and the external RAID system 702. The
external RAID system 702 typically has one or more disk arrays 704
that are controlled by a RAID controller 706. The RAID controller
706 is, in turn, operative with a high speed data transmission
mechanism, such as fiber channel controller 708. The fiber channel
controller 708 is connected to other similar devices, such as fiber
channel controller 712 of the server 714 via the control data
channel 710. Finally, the fiber channel controller 712 is connected
to the internal input-output system of the device, such as PCI bus
716 of the server 714. Other information handling systems have
different arrangements and combinations of internal and external
elements are possible with the present invention.
RAID controllers, like the Dell PERC2 and the Dell PERC3, which are
available from Dell Inc. of Round Rock, Tex., have specific
functional settings that can be varied to obtain maximum
performance for the type of operations the RAID array is most
likely to perform. There are a variety of policies that cover
different aspects of the RAID system, including the read cache, the
write cache, and the input/output ("I/O").
The implications and interactions of the various policy
combinations are sometimes difficult to discern. Moreover,
depending upon the type of loading on the server, the most
advantageous settings of these parameters may vary in real time.
For example, write policy specifies the cache write policy. The
operator can set the write policy to write-back or write-through.
In write-back caching, the controller sends a data transfer
completion signal to the host when the controller cache has
received all the data in a transaction. However, the write-back
setting is not recommended for various reasons. In write-through
caching, the controller sends a data transfer completion signal to
the host when the disk subsystem has received all the data in a
transaction. This characteristic is desirable and thus
write-through caching is the default setting for cluster mode.
Moreover, write-through caching has a data security advantage over
write-back caching, whereas write-back caching has a performance
advantage over write-through caching. Read-ahead enables the SCSI
read-ahead feature for the logical drive. The user can set this
parameter to No-Read-Ahead (No-Ahead), Read-ahead, or Adaptive.
Adaptive is typically the default setting. No-Read-Ahead specifies
that the controller does not use read-ahead for the current logical
drive. Read-ahead specifies that the controller uses read-ahead for
the current logical drive. Adaptive specifies that the controller
begins using read-ahead if the two most recent disk accesses
occurred in sequential sectors. If all read requests are random,
the algorithm reverts to No-Read-Ahead, however, all requests are
still evaluated for possible sequential operation.
Cache policy applies to reads on a specific logical drive. It does
not affect the Read-ahead cache. Cached I/O specifies that all
reads are buffered in cache memory. Direct I/O specifies that reads
are not buffered in cache memory. Direct I/O is the default setting
for typical SCSI systems. Direct I/O does not override the cache
policy settings. Data is transferred to cache and the host
concurrently. If the same data block is read again, it comes from
cache memory.
The overall performance of the RAID system is a function of the
load on the system and the different policies determine
characteristics such as write policy, read policy and whether the
data is cached on the board or in system memory. Each of the
policies can be mixed and matched among the policies of the other
aspects (read cache-write cache-I/O) of the RAID element to form an
overall RAID policy and hence performance for a given load. In the
example given above, there are 12 combinations of RAID policies as
shown in Table 1 below. Application of new or additional policies
with the present invention would increase the number combinations
possible. Each combination of policies has an affect on performance
of the RAID system and thus on overall system performance.
Consequently, the selection of the right combination of policies to
maximize some system performance parameter is achievable with the
present invention because it is flexible and can accommodate any
range of policies and combinations of policies.
TABLE-US-00001 TABLE 1 Policy Combinations Read Cache Write Cache
I/O No-Ahead Back Cached No-Ahead Back Direct No-Ahead Through
Cached No-Ahead Through Direct Adaptive Back Cached Adaptive Back
Direct Adaptive Through Cached Adaptive Through Direct Read-Ahead
Back Cached Read-Ahead Back Direct Read-Ahead Through Cached
Read-Ahead Through Direct
An example of policy versus performance is shown in FIG. 2 in the
form of a graph of number of clients versus aggregate megabytes per
second, which show the relationship of read throughput of two
server systems to the number of clients that are connected. The
appropriate RAID cache parameter settings for ultimate performance
varies depending on how many clients are making requests to the
server for disk access. Thus the present invention provides the
ability to independently control all of the available policy
settings in order to optimize performance of the system (or an
element within the system) for a perceived load on the system.
FIGS. 2 and 3 show the relationship of throughput of two DELL.RTM.
server systems versus the number of clients connected for a variety
of read and write cache policies. The DELL.RTM. servers are
available from the Dell Inc. of Round Rock, Tex. As FIGS. 2 and 3
show, the appropriate RAID cache parameter settings for optimum
performance varies depending on how many clients are making
requests to the server for disk access and the type of cache policy
chosen. In the case of FIG. 2, the two policies compared are the
adaptive cached back policy, and the no read ahead direct through
policy. In the case of FIG. 3, the two policies compared are the
direct back adaptive policy and the cached back adaptive policy.
Other policies can be used with equivalent effect with the present
invention, and this specification should not be viewed as limiting
in any way a particular cache policy or number of policy
combinations. Indeed, other cache policies may be developed from
time to time that further optimize a desired characteristic of the
information handling system, such as bandwidth, speed, or the like.
Selection of the desired optimizing characteristic (or set of
characteristics) is often best determined in real time based upon
the amount and character of the load on the servers. Server load
can be assessed by, for example, the number of clients that are
connected to the server by the network, and/or by the number of
active files that are open and being read/written from/to by the
clients on the network or other measures.
Statically setting these parameters means performance is
compromised for servers where the number of connected clients
varies. In the past, the cache policies were normally set in the
controller BIOS prior to operating system boot up. In some
instances, the cache policies are set by a GUI application executed
under control of the operating system. In either case, the RAID
settings are not dynamically altered under program control in
real-time or near-real-time.
An application or service running on a server can monitor the
number of connected clients, their open files and I/O request
status. Based on these conditions and previous measurements made
for the server class of machine, the RAID cache parameters can be
dynamically altered through vendor API calls to provide maximum
disk throughput as clients request and release control of files on
the system. Moreover, the number of client files that are actively
requesting data can also be monitored, and that data can be used to
affect the cache policy that is employed on a dynamic basis.
FIG. 4 illustrates a method for adapting, in a dynamic manner, the
cache policy for the RAID array based upon monitored conditions of
the network. Referring to FIG. 4, the method starts generally at
step 402. Thereafter, in step 404, a table of stored information
relating to the number of active clients versus the cache settings
is read. Typically, the tables that are stored are based on
experimental results by the vendor and/or network administrator
based on representative conditions. In other words, tables of
conditions such as those depicted in FIGS. 2 and 3 are stored can
act as templates that are made available to the application process
that monitors the network and sets the RAID cache policy. The
stored tables/templates can act as a collective memory of
experience that can be applied by the monitoring/directing process
to select the best cache policy that maximizes network bandwidth
and/or overall network system performance. Similarly, the
monitoring/directing process could also use one or more algorithms
that can predict the best cache policy to employ under any network
condition. Finally, alternate embodiments of the method of the
present invention can employ a combination of algorithms and table
template reference can be used to set the cache policy in a dynamic
manner.
Referring back to the embodiment depicted in FIG. 4, after the
stored tables of network performance based on the number of clients
and cache policy is read (in step 404), the load on the network is
determined in step 406. The load on the network can be determined
from one or more factors, such as the number of client devices in
operation, the number of open files in use, etc. In step 408, the
tables that were read (in step 404) are indexed according to the
network load that was determined (in step 406) in order to
determine the best cache policy that maximized desired performance.
In alternate embodiments, the algorithm or algorithm/table
combination would be accessed or indexed to provide the same
selection of cache policy. The cache policy that was identified in
step 408 is then applied to the one or more RAID disk systems
instep 410. Thereafter, an optional delay may be implemented in
step 412 to clear out the cache (employing the previous cache
policy) or for other purposes. The method then repeats steps 406
through 412 as illustrated in FIG. 4 so that cache policies may be
periodically or continuously updated.
FIG. 5 illustrates a network 500 that implements an embodiment of
the present invention. The network 500 employs a server 502 that
services information to and from a number of clients, such as
personal computer 530, workstation 532, laptop computer 534, and
wide area network 536 along a network connectivity mechanism 524,
such as an Ethernet link as illustrated in FIG. 5. Within the
server 502, there are one or more client network connections 503,
such as a network interface card. The server 502 is also equipped
with a RAID controller 505 that controls one or more RAID elements,
such as a hard disk or other mass storage device. The RAID load
monitor 520 is operative with the client network connections 503
and the RAID controller 505 as illustrated in FIG. 5. The RAID load
monitor 520 is constructed and arranged to implement the method of
the present invention, such as the embodiment illustrated in FIG.
4. The RAID load monitor 520 can thus access one or more tables
that are stored on the RAID system that is operative with the
server 502 via, for example, the RAID controller 505. Similarly,
the RAID load monitor 520 can determine the number of files open
and clients attached via the RAID controller 505 and the client
network connections element 503. The RAID load monitor is thus in a
position to determine which cache policy best maximizes the desired
performance characteristics of the network and can have that policy
implemented by the RAID controller 505.
An alternate embodiment of the present invention is illustrated in
FIG. 6. In thisalternate embodiment, the clients 630 through 636
are serviced by a server farm that consists of multiple servers 602
through 610 as illustrated in FIG. 6. A load balancer 620 is used
to distribute the load associated with the network 624 and clients
630 through 636. In this example, a load balancer 620 is used.
However, other devices, such as a router, server, grid master,
cluster master or other device could be substituted for the load
balancer 620 with equivalent effect. The RAID load monitor 622 can
be implemented on the load balancer 620 so that the RAID load
monitor is in a position to monitor the number of clients serviced
by the system 600, and to change the RAID cache policy used by the
various servers 602 through 610 by implementing the method of the
present invention as illustratively described in FIG. 4. The
configuration offing. 6 is further useful in that the RAID load
monitor 622 can tailor the RAID cache policy for each of the
individual servers 602 through 610 individually (or collectively)
so that additional tailoring and optimization of the network 600
can be achieved.
The invention, therefore, is well adapted to carry out the objects
and to attain the ends and advantages mentioned, as well as others
inherent therein. While the invention has been depicted, described,
and is defined by reference to exemplary embodiments of the
invention, such references do not imply a limitation on the
invention, and no such limitation is to be inferred. The invention
is capable of considerable modification, alteration, and
equivalents in form and function, as will occur to those ordinarily
skilled in the pertinent arts and having the benefit of this
disclosure. The depicted and described embodiments of the invention
are exemplary only, and are not exhaustive of the scope of the
invention. Consequently, the invention is intended to be limited
only by the spirit and scope of the appended claims, giving full
cognizance to equivalents in all respects.
* * * * *